Dhaka’s air quality has become “very unhealthy” as the capital of Bangladesh has again topped the list of world cities with the worst air quality. The capital's Air Quality Index (AQI) score was recorded at 248 at 9am on Monday. Pakistan’s Lahore and Ukraine’s Kyiv occupied the next two spots, with AQI scores of 222 and 168, respectively. Read: Poba urges to control sound pollution An AQI between 101 and 200 is considered 'unhealthy', particularly for sensitive groups. Similarly, an AQI between 201 and 300 is said to be 'poor', while a reading of 301 to 400 is considered 'hazardous', posing serious health risks to residents. AQI, an index for reporting daily air quality, is used by government agencies to inform people how clean or polluted the air of a certain city is, and what associated health effects might be a concern for them. In Bangladesh, the AQI is based on five criteria pollutants -- Particulate Matter (PM10 and PM2.5), NO2, CO, SO2 and Ozone. Dhaka has long been grappling with air pollution issues. Its air quality usually turns unhealthy during winter and improves during monsoon.